Several months later, Muniz took charge of an engineering team on DS9 after O'Brien was recovering from his Argrathi punishment. (DS9: "Hard Time")

In early-2373, Muniz was part of a Starfleetsurvey team from DS9 that traveled to the Gamma Quadrant planetTorga IV to assess the possibility of establishing a mining operation to extract some of the planet's rich deposits of cormaline. A Dominion ship crashed on the planet and was later followed by another who destroyed the team's runabout and landed Jem'Hadar troops. Muniz was wounded by the Dominion weapons, but was saved by O'Brien and Worf and taken into the ship. The anti-coagulant in the Dominion weapons soon took their toll on Muniz and his bleeding continued.

O'Brien and Worf clashed after Worf told him that Muniz was near death. As time went on, Muniz soon lost feeling in his legs and became delusional, believing he was watching a carnival with his father. Muniz eventually died of his wounds during the crew's attempt to use the ship's engines to escape.

After the Defiant arrived, rescued the crew and towed the Dominion ship off the planet and back to the Alpha Quadrant, O'Brien sat with Muniz's body, performing a traditional Irishwake. He was joined by Worf who commented on its similarities to the Klingon tradition of ak'voh.

During his time on Deep Space 9, Muniz eventually became a good friend of Chief O'Brien, whom he called jefe, Spanish for "chief". O'Brien affectionately called him "Quique". (DS9: "The Ship")

The script for "Starship Down" describes Muniz as simply, "a young enlisted engineer". Of a scene in the Defiant's engine room, it makes note of the fact Muniz and the other engineering crewmen didn't go to Starfleet Academy, saying, "they're not as polished as our people, and they have their own work habits and codes of behavior." [1]

In the script for "The Ship", Muniz is further described as, "a young human crewman with an easy, infectious smile." [2]

The choice of bringing back Muniz for "The Ship" was an important one for the writing staff but looking back, they didn't think it quite worked out the way they had hoped. "Ira [Steven Behr] wanted to establish that there was an inner circle amongst the engineers, guys who hung out together," said writer Hans Beimler, "and that there was a special place in the heart of O'Brien for his engineering guys. Muniz was one of those guys. We tried to build a relationship between the two of them at the beginning." Commenting on that relationship, Behr explained, "The whole idea was to show that the engineers, the tech guys, have a brotherhood that's different from just the old Starfleet brotherhood. We wanted to bond O'Brien with this guy and have it mean something. But the scenes didn't play like two guys who were really comfortable with each other. It wound up being about O'Brien and a guy who's dying. The audience never came to care enough about Muniz because they didn't see O'Brien's investment in Muniz." (Star Trek: Deep Space Nine Companion, p.371)